A group of horsewomen have filed a products liability lawsuit in federal court in California, suing the manufacturer of the commonly used equine topical ointment “Fura-Zone,” claiming repeated exposure to the ointment caused them to suffer reproductive and fertility problems, including ovarian cysts and fibroids.
Fura-Zone is a topical antibacterial ointment containing the active ingredient nitrofurazone (“NFZ”). NFZ is an odorless, pale-yellow antimicrobial agent in powder form that treats and prevents surface bacterial infections in wounds, burns, and cutaneous ulcers in horses. Equestrians administer Fura-Zone topically by applying it directly on lesions with a spatula or first on a piece of gauze. According to the Fura-Zone instructions, the product can also be used as a sweat by lathering Fura-Zone around the affected joint, covering it in plastic wrap, and then applying a bandage. When applying a sweat, it is common to mix Fura-Zone, an NFZ-based product, with dimethyl sulfoxide (“DMSO”), a colorless liquid that aids the transportation of toxic compounds across skin, thereby inducing toxicosis from the NFZ. The plaintiffs allege that these instructions permit exposure through touch and inhalation.
According to the SAC, studies dating back to the 1960s show that NFZ produces mammary tumors in rats and ovarian tumors in mice. Studies from the National Toxicology Program found “clear evidence” of carcinogenic activity of NFZ for female rats and mice, and “equivocal evidence” of carcinogenic activity of NFZ for male rats. Further, scientists have explained that NFZ not only causes cancer but also makes existing cancer progress at a much faster rate because NFZ spurs cell proliferation, promoting progression in carcinogenesis.
The lawsuit alleges that scientific knowledge of NFZ’s toxicity has led to increasing regulations of its use. In 1991, the Federal Drug Administration (“FDA”) banned NFZ for use in poultry and swine consumed by humans because of cancer risks. In 2002, the FDA banned the topical use of nitrofurans on food-producing animals because studies proved that cattle treated with NFZ had carcinogenic residue in their milk and tissues. California’s Proposition 65 includes NFZ in its lists of carcinogens and/or reproductive toxicants as a reproductive toxicant.
In their lawsuit, the women admit they understood Fura-Zone was intended to be used on horses. However, they contend they were not aware they were risking reproductive harm by applying Fura-Zone in a manner prescribed by the product itself. The women all allege they routinely used Fura-Zone as an antibiotic ointment, applying it to horses within their care.
Despite early defense motions to dismiss, the case remains pending.
Pitzen v. Atl. Animal Health, Inc., No. 25-cv-0196-ABJ-DEB, 2026 U.S. Dist. LEXIS 103878 (S.D. Cal. May 11, 2026)
